Snohomish County Sheriff’s detectives believe a mechanical failure caused the accident that killed a 42-year-old Bothell man who was driving a motorcycle at the Evergreen Speedway on Sept. 5.

Ed Ritter was going an estimated 97 mph when the motorcycle he was racing crashed into the side of a bus.

“Based on my observations of the scene and damage to the motorcycle, I believe Ritter likely encountered a catastrophic mechanical failure at or near the end of the drag course resulting in the rear wheel of the motorcycle becoming locked,” said Sheriff’s Office Detective Marc Monson.

Monson said that the locking of the rear wheel would explain the long single tire mark that was observed leading from the end of the course to the point of impact with the bus.

“Once the rear tire became locked, Ritter would have been able to continue sliding in a somewhat straight line but would have lost the ability to turn the motorcycle to avoid running off the track and into the parked bus,” Monson said.

Initial reports indicate that this was a new motorcycle for the rider and that he overshot the track.

The bus was one of several parked at the track for other speedway events, including a figure-eight demolition derby the night before.

No one was aboard the bus and it was stationary at the time of the accident.